1. Field of the Invention
This invention is directed to a tool for exerting an upward force on another tool that may have become stuck in an oil or gas well. Such tools are commonly referred to as “jars.” Typically jars include a connecting device that is released at a certain level of force being applied to the line to cause a hammer to strike an anvil surface within the tool. The present invention is directed to an improvement in such a device
2. Description of Related Art
The sticking of drilling or production equipment in an oil or gas well bore may be eliminated by delivering an upward axial blow to unstick the equipment. Downhole tools known as “jars” have been used in such situations. One type of jar is a “drilling jar.” Another type of jar is a “wireline jar.” In the case of a wireline jar, a series of impact blows is delivered to the stuck equipment by manipulation of the wireline. Wireline jars typically have an inner mandrel and an outer housing telescopically coupled together for relative axial, sliding movement. The mandrel carries a hammer and the housing carries an anvil. By directing the hammer to impact the anvil at high velocity, a substantial jarring force may be imparted to the stuck equipment, which is often sufficient to jar the stuck equipment free.
Examples of prior art jars are described in U.S. Pat. Nos. 6,988,551; 7,290,604; and 7,311,149.